1. Field of the Invention
The present invention relates to a light guide changing light emitted from a point light source to a linear form and emitting the linear light beam, an illuminating device comprising the light guide, and an image reading apparatus comprising the illuminating device.
2. Description of Related Art
As an example of conventional illuminating devices, a device disclosed by U.S. Pat. No. 8,279,499 is known. As shown by FIG. 11, the illuminating device disclosed by U.S. Pat. No. 8,279,499 comprises a light source 640. Light emitted from the light source 640 is split by a splitter 650 into two. One of the split light beams enters light guide 660a and the other thereof enters light guide 660b. 
The illuminating device 520, however, has a problem of not making effective use of the light emitted from the light source 640. The splitting portion of the splitter 650 for splitting the light to travel toward the light guides 660a and 660b comprises two inclined surfaces designed at an angle of a to each other. The junction of these inclined surfaces is actually formed as a curved surface due to the nature of molding or cutting. Light entering the junction is scattered thereon and/or passes through the junction. Accordingly, part of the light emitted from the light source 640 leaks from the illuminating device 520 without entering the light guides 660a and 660b. Thus, in the illuminating device 520, the junction of the inclined surfaces is a cause of low usage efficiency of the light emitted from the light source 640.